If victorious Caruana would become the first US world champion in four decadesCarlsen will be seen as the favourite as he is considered an expert at rapid chess.

However, former grand master Garry Kasparov tweeted that he thought the draw offer indicated the Norwegian was losing his nerve.

In the ordinary games, each player starts with a generous time bank of 100 minutes, and more time is added as the game progresses. That means it is possible to watch a grandmaster do nothing except stare at the board for several minutes.

But in the tie-breakers, four games are played with just 25 minutes on the clock, and 10 seconds added after each move.

If it is still a draw after that, two "blitz" games are played - with just five minutes per player and three added seconds per turn. In such circumstances, mistakes are much easier to make.

In the unlikely event that after two sets of blitz, the title is still tied, a sudden death variety called "Armageddon" is played.

In this chess game type, there will be a winner - a draw means a victory for the player wielding the black game pieces. To compensate, white gets more time on his clock - a minute more, but the pace is still as fast as a blitz game.